leetcode-Set Matrix Zeroes

Set Matrix Zeroes Total Accepted: 25064 Total Submissions: 80609 My Submissions Question Solution 
Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.


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Follow up:
Did you use extra space?
A straight forward solution using O(mn) space is probably a bad idea.
A simple improvement uses O(m + n) space, but still not the best solution.

Could you devise a constant space solution?

class Solution {public:    void setZeroes(vector<vector<int> > &matrix) {                int row1=1;        int col1=1;        int m=matrix.size();        int n=matrix[0].size();        //扫描第一行        for(int j=0;j<n;j++)            if(matrix[0][j]==0)                row1=0;        for(int i=0;i<m;i++)            if(matrix[i][0]==0)                col1=0;                                //扫描余下矩阵        for(int i=1;i<m;i++)        {            for(int j=1;j<n;j++)                if(matrix[i][j]==0)                    matrix[i][0]=matrix[0][j]=0;        }                //行置0        for(int i=1;i<m;i++)            if(matrix[i][0]==0)                for(int j=1;j<n;j++)                    matrix[i][j]=0;                //列置0        for(int j=1;j<n;j++)            if(matrix[0][j]==0)                for(int i=1;i<m;i++)                    matrix[i][j]=0;                            //第一行置0        if(row1==0)        for(int j=0;j<n;j++)            matrix[0][j]=0;                //第一列置0        if(col1==0)        for(int i=0;i<m;i++)            matrix[i][0]=0;    }};